Hi All
This comes after a facebook discussion on Australia Audio Trading group.
Apparently you can adjust the frequency bandwidths of Sennheiser wireless receiver units by soldering different value SMD resistor on the RF circuit Board .
This is handy for Australian users because in 2014 the Australian Government is selling off our frequency band (694-820MHz) to the digital world (Phone and TV services) so we won't be able to use our wireless mics if it's in that bandwidth.
We are trying to work out the SMD resistor replacement values to adjust the frequency band.
Sennhesier ex100 g1 conversation - YouTube
EW100 G1 unit below
This comes after a facebook discussion on Australia Audio Trading group.
Apparently you can adjust the frequency bandwidths of Sennheiser wireless receiver units by soldering different value SMD resistor on the RF circuit Board .
This is handy for Australian users because in 2014 the Australian Government is selling off our frequency band (694-820MHz) to the digital world (Phone and TV services) so we won't be able to use our wireless mics if it's in that bandwidth.
We are trying to work out the SMD resistor replacement values to adjust the frequency band.
Sennhesier ex100 g1 conversation - YouTube
EW100 G1 unit below
An externally hosted image should be here but it was not working when we last tested it.
Hmm, sorry to say, I highly doubt that this is true. I don't see how there's any way that a single resistor could change the band unless the 5 RF-style units on the board are the 5 different receivers, which would seem to be a very expensive way to provide boards. I'll have a look at work in a day or so, though I think ours are D as well.
Assuming the thing works in the obvious way (A pair of superhets), the resistors probably just configure the micro to program different PLL dividers, which is fine as far as it goes, but I bet there are also changes required to the input bandpass networks (Those L/C filters near the aerial sockets) and probably different parts in the VCO as well.
Tweaking the filters really needs a VNA or at least a scalar analyser and a noise source or tracking generator.
The VCO is a bit of a mystery without a diagram and could be anything from no changes required to a few capacitors and chip inductors to a complete replacement depending on the design.
Nothing insurmountable, but I have to ask is it worth the pain?
Regards, Dan.
Tweaking the filters really needs a VNA or at least a scalar analyser and a noise source or tracking generator.
The VCO is a bit of a mystery without a diagram and could be anything from no changes required to a few capacitors and chip inductors to a complete replacement depending on the design.
Nothing insurmountable, but I have to ask is it worth the pain?
Regards, Dan.
Not always. Often the front ends are designed to be wide-band, with most of the selectivity accomplished in the IF filters. This is so one board, with a simple resistor change (for the PLL), can be used in many markets.
This may or not be the case here, but it may be found that simply changing that resistor is good enough.
IMD is an issue in radio mics, so a little front end selectivity is generally seen as a good thing, but the 100 series is low end kit so I suppose it might well work that way.
I would expect a 10MHz or so wide input filter, 100+MHz would really surprise me.
One way to find out, change the resistor and plot the sensitivity across the new band.
73 Dan.
I would expect a 10MHz or so wide input filter, 100+MHz would really surprise me.
One way to find out, change the resistor and plot the sensitivity across the new band.
73 Dan.
I don't think the resistor mentioned makes any difference to how the system works.
The position of this resistor makes no difference because there is a common "rail" at each end of these resistors. Electrically there is no difference at all which of these positions the resistor is in, so the position cannot affect the performance in any way.
I don't think the value of the resistor has any effect on this either. I tried shorting the resistor out with a link and I removed the resistor. The receiver continued to work as a D Band receiver, nothing changed.
I think you will have to change the whole RF board to change frequency band. But why would you bother?
The position of this resistor makes no difference because there is a common "rail" at each end of these resistors. Electrically there is no difference at all which of these positions the resistor is in, so the position cannot affect the performance in any way.
I don't think the value of the resistor has any effect on this either. I tried shorting the resistor out with a link and I removed the resistor. The receiver continued to work as a D Band receiver, nothing changed.
I think you will have to change the whole RF board to change frequency band. But why would you bother?
Hi All,
This is Guclu, I am a local Sennheiser contact.
To change the frequency band in these first generation receivers you need to change the whole RF board. There is no short cut. The resistor mentioned in Deejaypk’s video is a visual indicator of the frequency band of the RF board.
Different frequency versions use different component values which optimise performance in the band the RF board is designed for. But visually you cannot tell them apart by those components, they are too small to see any differences and are hidden in the cans anyway. The resistor is loaded onto the board at the same time as the other components, but it has no electrical effect at all; it is not connected to the circuitry.
I hope this helps and if you have further questions, please get in touch.
Regards,
Sennheiser Australia
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.